Changing image texture as height increases and using colorRamp with image texture
Use different ramps, each one with a different increasing range, to map  the information from the $Z$ axis.

(The math node in this case is not doing anything, but can help you refine the placement and scale the coordinates for the z axis. The ramp node's range is confined to values from 0 to 1 so if your values exceed that range or are too small you might need to scale them)

Then, each one of the ramps can be used as controls a color mix between two different images, and then concatenated to mix new images in different heights of the mesh.